I really like two parts of a black tea and one part green tea for my KT base. But I like to use honeybush, rooibos, jasmine, darjeeling, yerba mate, irish breakfast, young hyson, pu-erh, assam and oolong teas, these are my core teas. You need to make sure your base tea does not include any oils as this can lead to mold development. Yemoos.com has a nice selection of base teas for KT. I love to add dried hibiscus flowers to the primary too, it never interferes other than the baby develops around the flowers, so a simple hibiscus broth can be added instead; then add orange slices and ginger to the secondary--amazing! Other than hibiscus I do not add any spices, flavorings, etc. to the base, these go in secondary.
Motto: quel che sara sara